Manufacture of cyclized rubber



to ordinary soaps which are the sodium salts of fatty acids and in which the fatty acid radical is the anion. The fatty acid residue produces the colloidal effect in both types of soaps.

Among the cationic soaps may be mentioned salts of quaternary ammonium bases, having a formula selected from the group consisting of /N\ R2 R4 and in which R1 is a member of the group consisting of the alkyl, alkylol, aralkyl and aryl-alkylol radicals having more than 12 carbon atoms; Rz, R3 and Ri are members of the group consisting of hydrogen and the lower alkyl, aralkyl, aryl and heterocyclic radicals, including derivatives of these groups, such as alkyl sulphonate, alkylamine and alkylol radicals, which tend to increase the solubility in water of the quaternary ammonium salt, and X is a member of the group consisting of the anions of water-soluble acids.

Examples of suitable cationic emulsiers are the bromide or chloride of the N-cetyl pyridinium-ion commercially available under the tradename Fixanol; the acetate or metho-sulfate of (dialkylamino ethyl) -fatty acid amides, known under the trade name Sapamine; and the alkali salts of methyloleylamide-ethylsulfate, known under the trade-name Igepon T. Others are the oleamide and stearamide of aminoethylethanolamine and the cocoanut oil fatty acid arnides of monoand di-ethanolamine. In general, every organic nitrogen compound, in which the nitrogen atom has a coordination number of 4, which is water-soluble, and where at least one of the substituents attached to the nitrogen atom contains a long chain hydrocarbon group and which is acid-stable in the sense given above, is a suitable stabilizer in the process of my invention.

It is almost impossible completely to describe the commercial synthetic surface active agents by naming a single chemical compound since in nearly every case the materials sold constitute a complex reaction mixture of several compounds produced in the chemical reactions by means of which they are produced. Reference can be made to Soap and Sanitary Chemicals, August,

r September and October 1949 and to the booklet entitled Synthetic Organic Chemicals United States Production and `Sales of Surface-Active Agents, 1948, published by the U. S. Tarii Commission, Washington, D. C., for lists of other cationic surface active agents which are use ful in my process. All of these agents are operative which have the properties set out above.

The concentration of cationic surface-active agent required to stabilize the latex depends largely upon the emulsifying power of the particular agent used. The usual range of concentrations is from about 1.5 to per cent. By reason of economy and of the undesirable properties which may be caused in the iinal product y by the presence therein of stabilizing agents, I prefer to use those stabilizing agents which are highly effective emulsifying agents and can produce the desired stabilizing effect when used 1n very small quantities.

It should be mentioned that acid latices, which have been produced in the prior art by the use of such dispersing agents as saponin, hemoglobin, casein, glyorrhyzin salts etc., are stable toward acids only up to concentrations of about 3 N. Whereas the minimum acid concentration required to produce cyclization corresponds to about 60 per cent sulfuric acid. ObviouslyY these agents cannot be used in the present process.

My process can be applied to all of the natural rubber latices as Well as to the cyclization of artificial latices of all unsaturated synthetic rubbers which are capable of being cyclized. This includes all rubbers which are polymers or copolymers of conjugated dienes, such as those prepared by the polymerization of 1,3-butadiene alone or copolymerized with other polymerizable monomers, such as styrene, vinyl naphthalene, the alpha methylene carboxylic acids and their esters, the nitriles, such as acrylonitrile, amides of acrylic acid, methyl acrylate, methyl methacrylate, methacrylonitrile, methacrylamide, isobutylene, methyl vinyl ether and the like. Several artificial latices prepared from these synthetic unsaturated rubbers have appeared on the market having dry rubber contents within the range of from about 30 to 65%. The rubber in these products can be cyclized by my process. This process is applicable to all aqueous dispersions of unsaturated rubbers with the particles in some cases being locculated or in the form of a wet coagulum.

It is evident that there are numerous factors which will influence conditions for the most satisfactory operation of the present invention, the actual limits of which cannot be established except by a detailed study of each set of starting materials and the intermediate and finished products involved.

The term cyclized rubber is understood to mean and include each cyclized product of the operation of this invention having the same ratio of carbon and hydrogen as the rubber from which it was prepared but with a decreased unsaturation as compared With such rubber.

The introduction of sulfuric acid into a stabilized rubber latex first produces a certain acid concentration in the aqueous phase depending upon the strength of the acid used and the rate of its addition. The stronger the acid the slower it should be added since coagulation and over heating may be produced by the too rapid addition of oleum, for example. During the addition of the acid the reaction mixture should be agitated to maintain a uniform temperature throughout, with adequate cooling to prevent the temperature from rising too high. The reaction time may vary from about 30 minutes to over 10 hours depending upon the starting materials, the reaction conditions and the degree of cyclization required. An extended cyclization at higher temperatures may cause the cyclized rubber to be precipitated in a iinely divided condition.

After the cyclizing agent reaches a minimum concentration of approximately 60 per cent by weight it begins to react with the rubber globules in the latex, with the rate of reaction depending upon the pressure and temperature at which the reaction mixture is maintained. With an acid concentration of about per cent, for example, cyclization requires over 24 hours at room temperatures whereas a concentration of 60 per cent requires an operating temperature of at least C. if the time of reaction is to be held to a reasonable figure. The practical range of acid n.eonoentrationszisofrom aboutfO totopenzcent .by weghtrwithtemper'atures ranging correspondabove1140 cannot beeemployed ksince carbon- ,.:ization .isilikely 1to .occur atA .such temperatures.

.The factors of iltime, .pressure Land y.temperature .may -be maintained; for any desired `cycle fof operation .or :changed at any .time during` .the

...Operation voflthezfproeess ,to obtain-.the .desired :degree :of cyclization. Thermost v,practical oper- .ating .periods .arewithin .the .range-.of .fromebout 230..minutes to v.10 thQurs.

The .proper .operating conditions :be .judged '.from .thegfellowine .table rwhiehteivesithe results obtained under different conditions:

Tem Time .uratedness of Ppercent B2S/O4 'Conc' '11195. 'inhours product. ""'Raw .latex :equals 100% 70 .l0 '33 80 ,5 25 90 "2. 5 v'20 .2100 ..1. 5 '12 .70 r3. 5. 30 70 '2. 5 26 Thefcrm .in .which the cyclized rubber is present" in `th'e".disperfsion` is determined b y the extent of agglomeration of the cycliaed'r'ubber .particles 'TIf anyfsubst'antial .agglomeration oc- .filocculation arid/ or sedimentation, combined, if

desired,with'centrifugingor :other methods of .i'reatrrient-` The'...separatio n Yo'f solid l cyclized rubber'. may be" effected .by the addition to .the 'dispersion of a precipitant which may be an organic non-solvent, such as alcohol or toluene or in some instances, water. In contradistinction to most commercial cyclized rubber, the solid cyclized rubber recovered in this process is in a finely divided powder form.

My invention can be explained in greater detail by reference to the following specic examples which represent practical operating embodiments of my process.

Example 1 A natural rubber latex having a dry rubber content of 60% was stabilized by adding to 20 m1. thereof 10.5 ml. of a 6% solution of cetyl pyridinium bromide. 54 g. of concentrated sulfurie acid were added to the stabilized latex so that in the serum the acid concentration was 75%. The mixture was then maintained at a temperature of about 80 C. for about 2 hours, after which the reaction mixture was cooled and the cyclized rubber precipitated therefrom by the addition of alcohol followed by drying. l2 g. of an excellent grade of cyclized rubber were recovered in this manner.

Example 2 150 g. of 60% latex were mixed with 75 g. of water. Herein 6.4 g. of a cetyltrimethyl- The ammonium:- nromideesomuon (trade-.mark Wul- :.castabv '-M. tof the LI.- :Co-.1.) .were Lpnredxwhile stirring. 'Ifherexwasnow .1.1A,% emulsifyingagent calculated` :on the rubber. Whilecoolingzfand y.stirring 420 g. ofconcentratedsulphuric.acidwvere added, 4.i...e. .75% V.calculatedion the .waterlzphase This .mixture ;was {maintainedzat '90 .C tforLtWo Example 3 100 g. 60% latex were stabilized wth.;.a-:; .solu

...tion lof .1.2 '-lg.'cetylpyridnium bromide Y(trademark Fixanol ,C ofthe. I..-C. 1.1.) in `aug. wa-ter.

' .There was new 2% *.Fixanol .C .calculatedcon the ".rubber.

296 ,.gg. of concentrated: sulphuric/.acid were added vwhile cooling .and stirring, .so-that .the acid concentration inithezwaternphase: was 801%. VThis mixture .wasimaintainedzat '10 LC.

,andsamplesof :hllog weretakenafter 1/i hour. 3A hour .and W2 hours.

The .cyclo Vrubber .was separated .off by pouring out .the 4reactionximix- -ture `into `the ,doublequantity of boiling Ywater.

The products weredried. .Thennsaturatednesses were-.45. dri-'and 25 resp.

VEmotif/ale gt4 20 g. 60% latex were stabilizedwithrasolution of 1.2 g. Ndiethyl-;amino,ethyl oleylamideimethosulphate `(trade-markSapamine1M. S. of.C,i ba) in 8 e. Water. Eherezwes now 10% Yof Lemulsify- ,ing agentcalculated onfthe-,rubben fldeletoeigg. of concentrated sulphuricyacd .were added .While cooling and stirring. .v-Thisgrnixture was..ma intained .at 1oo..c. `for y5 hours. .After ,eooungthe mixture -waseeparated off by A`pouring out .into ..100 g. water-,and subsequent .shaking pu/ith 30gg. o f chloroform. `The product was driedandgthereupon the unsaturatedness was determined. This was 21.

The procedures usedfin the above examples can be applied to thef'cyclization of latices prepared from all unsaturated synthetic rubbers which are capable VAof being cyclized.

While I have described what I consider to be the most advantageous-"smbodiments of my process it is evident, of course, that various modifications can be made4 in the specic procedures which have been described without departing from the purview of this invention. Thus, while it is possible to conduct my cyclizing process with diluted latices, it is more advantageous to employ latices having a concentration of at least 25 per cent rubber content. This is more economical in that there is a saving in cyclizing agent as well as stabilizing agent. When a rubber flocculate is used the dry rubber content of the aqueous dispersion may range up to about per cent by Weight.

The cyclorubber may be precipitated from the reaction mixture, the precipitate may be Washed (in order to remove the sulphuric acid etc.) and the cyclorubber may then again be dispersed in water. In this manner a pure aqueous dispersion of cyclorubber is obtained.

The precipitated and puried solid cyclized rubber obtained in my process may be dried and used directly in powder form or the aqueous dispersion of cyclized rubber recovered in my process can be puried by any of the conventional methods used for purifying latex and then used as a cyclized rubber latex for industrial applications.

In order to modify the properties of the cyclized rubber latex and the cyclized rubber to be recovered therefrom, softeners (e. g. phthalate), plasticizers, stabilizers, active or inert fillers, vulcanization ingredients, pigments and the like can be added to the original rubber latex, the cyclized rubber dispersion or the solid cyclized rubber.

The cyclized rubber may be vulcanized with materials, such as sulfur, suldes, Sz-Clz, KSOsClz and `SOzClz The cyclized rubber in the aqueous dispersion may be vulcanized before its separation therefrom by the use of vulcanizers which are not affected adversely by the acidity of the dispersion.

The cyclized rubber product is suitable as an adhesive and as an insulating material. The addition of cyclized rubber to synthetic or natural rubber can improve various properties of the vulcanization. Cyclized rubber can be used also as a substitute for gutta-percha in the manufacture of golf balls. Cyclized rubber may be used in the manufacture of water-proof paper. Cyclized rubber can be used also in the manufacture of paints and lacquers, since a solution of cyclized rubber may be evaporated to give a glossy ilm which hardens on exposure to air.

Other modifications of my invention which fall within the scope of the following claims will be immediately evident to those skilled in the art.

What I claim is:

1. In the manufacture of cyclized rubber, the process which comprises adding to an aqueous latex of an unsaturated rubber capable of being cyclized and selected from the class consisting of natural rubber and the synthetic rubbery homopolymers and copolymers of conjugated diolen hydrocarbons, a small amount of a cationic surface-active agent capable of stabilizing the latex in the presence of concentrated sulfuric acid and having a formula selected from the group consisting of and wherein R1 is a member of the group consisting of the alkyl, alkylol, aralkyl and aryl-alkylol radicals containing more than 12 carbon atoms; R2, Rs and Rr are members of the group consisting of hydrogen and the lower alkyl, aralkyl, aryl and heterocyclic radicals, while X is a member of the group consisting of the anions of Water-soluble acids; adding sufficient strong sulfuric acid to produce an acid concentration within the range of from about to 90 per cent by weight and heating the mixture at reaction temperatures below about C. for a period of from about 30 minutes to l0 hours to cyclize the rubber, whereby a dispersion of finely-divided cyclized rubber is obtained.

2. The process of claim 1 wherein the latex has a concentration of rubber within the range of from about 25 to 80 per cent by weight.

3. The process of claim 1 wherein the cyclizing temperature employed is within the range of from about 50 to 120 C.

4. The process of claim 1 wherein the surfaceactive agent is added in the amount of from about 1.5 to l0 per cent based on the dry rubber content.

5. The process of claim 1 wherein the surface active agent is selected from a class consisting of cetyl pyridinium bromide and chloride.

6. The process of claim 1 wherein the cyclorubber is precipitated from the reaction mixture, the precipitate is washed and the cyclorubber so obtained is then again dispersed in water.

GERARDUS JOHANNES VAN VEERSEN.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,853,334 Bruson Apr. 12, 1932 2,005,320 Konrad et al June 18, 1935 2,040,460 Becker et al May 12, 1936 2,046,015 Bunbury et al June 30, 1936 2,265,324 Spence Dec. 9, 1941 2,536,789 Van Amerongen Jan. 2, 1951 2,555,068 Van Veersen May 2, 1951 

1. IN THE MANUFACTURE OF CYCLIZED RUBBER, THE PROCESS WHICH COMPRISES ADDING TO AN AQUEOUS LATEX OF AN UNSATURATED RUBBER CAPABLE OF BEING CYCLIZED AND SELECTED FROM THE CLASS CONSISTING OF NATURAL RUBBER AND THE SYNTHETIC RUBBERY HOMOPOLYMERS AND COPOLYMERS OF CONJUGATED DIOLEFIN HYDROCARBONS, A SMALL AMOUNT OF A CATIONIC SURFACE-ACTIVE AGENT CAPABLE OF STABILIZING THE LATEX IN THE PRESENCE OF CONCENTRATED SULFURIC ACID AND HAVING A FORMULA SELECTED FROM THE GROUP CONSISTING OF 